Arcanobacterium, Haemolyticum, Corynebacterium, Osteomyelitis
Arcanobacterium haemolyticum (previously Corynebacterium haemolyticum), a facultative anaerobe, Gram positive rod was first isolated from United States servicemen and indigenous populations of the South Pacific in 1946. Early reported cases detailed A. haemolyticum as a causative pathogen for exudative pharyngitis (most commonly in adolescents) and cutaneous infections. Osteomyelitis caused by A. haemolyticum has been described in less than five cases in the literature. Here, we describe our experience in diagnosing patient with osteomyelitis caused by A. haemolyticum.
A 30-year-old man with a history of peripheral neuropathy, diabetic foot ulcers, methicillin-resistant S. aureus osteomyelitis and amputation of the left second distal phalanx, who presented with a malodorous and painful plantar ulcer. Physical exam showed erythematous, edematous distal left foot and 3cm x 0.5cm x 2mm plantar ulcer with necrotic tissue and serosanguinous drainage. Labs revealed elevated inflammatory markers. Left foot X-ray showed previous amputation of the second distal phalanx, soft tissue swelling and indistinctness of the cortex of the 3rd distal phalanx, consistent with osteomyelitis. He underwent intraoperative debridement and resection of the distal second metatarsophalangeal joint. Intraoperative wound and bone cultures grew aerobic gram-positive bacilli with few diphtheroid. Histochemical analyses confirmed Arcanobacterium haemolyticum three days from the procedure. He was discharged home on a six-week course of IV clindamycin with wound VAC.
A. haemolyticum infections can be separated epidemiologically into two distinct subsets. Healthy adolescents presenting with upper respiratory tract infections and immunocompromised patients presenting with systemic serious infection. It is often overlooked or misdiagnosed due to its slow growth and features similar to other pathogens. Initial microbiology reads that show mixed flora, including gram-positive rods and diphtheroid bacilli, are part of the normal flora of the skin. A. haemolyticum’s distinct colony features typically are seen after 72 hours of incubation.
Gram-positive organisms, including Staphylococcus aureus, b hemolytic Streptococcus, and coagulase-negative Staphylococcus are the most common cause of osteomyelitis. A. haemolyticum is another gram-positive organism and the causative agent of osteomyelitis that is less commonly known. However, differentiation of A. haemolyticum from other gram-positive organisms is essential for a proper management and appropriate antibiotic treatment.